It is known for such electric motors to be controlled as a function of a temperature measured on the internal combustion engine, preferably in association with regulation of the real speed of the electric motor as measured by means of suitable sensors, such as Hall effect sensors.
In known methods, regulation is generally performed using a control loop operating on a difference between a setpoint signal representative of an operating parameter of the electric motor and a measured value of said parameter. The reaction speed of the regulation loop depends on its gain which is generally less than unity. Unfortunately, the setpoint value for a fan unit can vary frequently, in particular in stop-go traffic in which the driver alternates between accelerating and slowing down. Existing systems are then not very satisfactory for regulating the speed of the fan unit.
In a regulation loop that possesses low gain, the time needed for reaching the value desired for the operating parameter is too long compared with the frequency at which the setpoint is changed, such that the fan unit does not reach the setpoint before the setpoint changes.
Conversely, in a regulation loop that possesses high gain, the fan unit reaches the setpoint, passing in alternation through values that are less than and greater than the setpoint with sudden changes of speed that are particularly noisy and that are perceived by the user of the vehicle and are detrimental to user comfort.